1. Field of the Invention
The present invention relates to antenna systems, and more particularly, to a three-dimensional geometric space loop antenna for use in a confined space.
2. Description of Background Art
In general, the size of an antenna is dependent upon the wavelength and frequency of operation. For example, a one-quarter wavelength antenna operating in the radio frequency range (e.g., 27 MHz) would have a length of approximately 2 to 3 meters. This length of an antenna implicates a minimum amount of physical space that the antenna occupies. As such, various techniques have developed in an effort to reduce the physical space consumed by an antenna
One such technique involves simply shortening the length of the antenna conductor so it takes up less physical space. However, the space savings afforded by this technique comes at the cost of decreasing transmission or reception power for the communication signal thereby affecting the transmission range of the antenna. This range limitation problem is particularly so for antennas operating in the radio frequency range (approximately 1 MHz to 1 GHz). As such, this technique is not always desirable or practical. One solution to this limitation on transmission range is to increase signal power to the antenna. Such increased power comes at the cost of system efficiency, though, and may also be undesirable and/or impractical.
Another technique requires a departure from the conventional dipole shape of an antenna. Loop antennas can be circular, square, rectangular or other planar-type shapes. The loop of the antenna can be comprised of a number of turns. These turns are parallel planar to each other. For example, a two turn loop antenna could be etched onto a printed circuit board where the two turns of the loop are on one side of the printed circuit board. As such, a lengthy antenna conductor can therefore be contained in approximately the space of one loop. However, the diameter of the loop still may require a significant amount of physical space. This reduces the space available for electronic components necessary for the functionality of the transmitting/receiving device (e.g., a wireless (or cordless) mouse or keyboard). Decreasing the size of the loop diameter will decrease the transmitted or received communication signal power. As such, less signal voltage is presented to the receiving device. A significant size limitation, therefore, still exists for such antennas.
Other known antennas suffer from similar problems. For instance, the helical or spiral antennas compact the length of an antenna conductor into a series of parallel planar turns, where each of the turns in this series exists about a common axis. Thus, the physical space reduction afforded by antennas such as the loop, helical, spiral, and dipole antennas is limited in part based on the inherent uniformity that exists in these antenna designs, as well as antenna performance criteria.
In direct conflict with this inherent space limitation of conventional antenna designs is a growing desire for ergonomic housing designs that are more sleek and compact in form, such as in wireless mice. Within such ergonomically designed wireless devices, there is a smaller printed circuit board. This results in a reduction of the overall usable space on the printed circuit board, which in turn reduces the space that is available for the etched loop antenna having a length and turns sufficient to provide acceptable antenna range and performance.
Therefore, there is a need for an antenna design that provides high quality transmission and reception performance characteristics, wherein the antenna design can be efficiently implemented in a limited amount of physical space.
The present invention includes an antenna system having an antenna loop of which a portion of the antenna loop is configured in a different three-dimensional geometric space than another portion or portions of the antenna loop. In one-embodiment, the antenna loop is configured to provide good communication signal transmission and reception characteristics within a small (or confined) internal space in which a large antenna is unwieldy and undesirable. For example, the antenna loop may be housed within a small form factor cordless electronic device, such as a cordless pointing device or a universal control device, where surface area and volume are constrained by size and ergonomic constraints.
An advantage of the present invention is that it provides a flexible antenna loop in which the overall size (length) of the antenna is increased by moving a portion of the antenna loop into another space of a three-dimensional geometric space. For example, an antenna loop may have more than one portion, each of which is coupled together to form a single antenna loop having a larger length than, for example, conventional two-dimensional antenna loops. Increasing the length of the antenna loop enhances the quality of communication signals that are transmitted or received by the antenna system. The increase in the length of the antenna loop allows the antenna system to be used in small space or volume devices in which lower frequency ranges, for example, the below approximately 100 MHz range, are desired. The use of lower frequency ranges in such devices provides additional advantages such as decreased electronic circuit complexity.
The features and advantages described in the specification are not all inclusive and, in particular, many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter.